Blender Git Loki

VSE: Fix image adding inconsistency

When adding images with operator, image file path is split into filename
and directory passed to load function in name and path fields of
SeqLoadData struct. This is because when loading images directory
and filenames are split.

RNA API function passes whole path in path filed.

Apart from loading API inconsistency, this causes initial image loading
to fail, so strip resolution is not set. Also name field of SeqLoadData
should be reserved for strip name.

Let operator code concatenate and split filepath when needed so loading
API can be consistent with RNA API and also between strip types.

Reviewed By: sergey

Differential Revision: https://developer.blender.org/D10818